Amateur Comet Hunters Revel In the 'World's Slowest Sport'

It's been a tough winter for Dennis di Cicco. His complaint, however, has less to do with a snowy driveway than with cloud-shrouded skies.

Mr. Di Cicco is one of a handful of people worldwide who dedicate their spare evenings (cloudless and moonless, if you please) to looking for comets and asteroids - the leftovers from the solar system's creation. Their backyard tools range from simple homemade telescopes on sturdy mounts to elaborate observatories where computers drive the 'scopes and analyze their images.

The potential scientific payoff of what they discover can be enormous. Comet Hyakutake, still visible in the Northern Hemisphere, already is surprising professional scientists. Last Thursday, for example, United States and German researchers using Germany's ROSAT satellite reported the first detection of X-ray emissions from a comet. Now, researchers have to find explanations for the phenomenon.

Discovering and observing comets and asteroids remains one of the few scientific fields in which amateurs, using modest equipment, can make an important contribution. Most modern observatories and their huge telescopes are designed and funded to peer to the edges of the known universe, not search our celestial backyard. Yet comets and asteroids have had a dramatic impact on life on Earth, as crater records attest.

"I'm very much impressed by what the amateurs are accomplishing," says Thomas Gehrels, a professor of planetary science at the University of Arizona and head of the Spacewatch project, a full-time effort to monitor comets and asteroids. He notes that even amateurs are now using the latest digital techniques to spot their quarry.

Di Cicco is one of those. Images from his 11-inch telescope are captured by a detector using charged-coupled devices, the digital equivalent of camera film. Even from his relatively light-polluted location in a Boston suburb, he says his 'scope can spot faint objects that once were the province of Mt. Palomar's 200-inch telescope near San Diego, Calif.

Di Cicco, who by day works as an associate editor at Sky and Telescope magazine, focuses on spotting asteroids. "I've always been an observer," he says, adding that he built his first telescope when he was 13 and his first observatory when he was 14. "Initially, I never envisioned discovering something; that was never my driving force."

Instead, he was content with pinpointing the positions of known asteroids and reporting those positions to the International Astronomical Union. The IAU gathers observations from amateurs and professionals worldwide and uses them to continually refine its calculations of asteroid and comet orbits. It took three observations to establish the orbit of Shoemaker-Levy 9, which buried itself in Jupiter in 1994; it took 200 observations to foresee the collision.

In the process of observing the asteroids, Di Cicco discovered eight in the course of one year. These, he acknowledges, whetted his appetite, and he now has 40 discoveries to his credit. For Di Cicco, the chase, "capture," and confirmation of discoveries take place in the relative comfort of an elaborate home-built backyard observatory, which boasts an office, darkroom, and observing platform for his computer-operated telescope.

For others, the hunt is truly an outdoor experience. "At 5 degrees, it gets hard," says computer specialist Michael Rudenko, referring to the long winter nights spent observing from his backyard in Amherst, Mass. "In New England, you have to be ready when the sky is. If the sky was clear and the moon wasn't up, I was out."

Mr. Rudenko, a research associate in the astronomy department at the University of Massachusetts at Amherst, bagged the first of his three comets from his backyard in 1984. "I thought that it would come after a long night of observing," he recalls, "But it came on my second sweep of the sky, in about 10 minutes."

It also was a first for David Levy, a noted amateur comet hunter who shares the credit for comet Levy-Rudenko. "I spent 19 years and about 900 hours before the eyepiece" before that discovery, says Mr. Levy, who does some of his observing atop a stepladder beside his telescope in the backyard of his home outside Tucson, Ariz. Since then, Mr. Levy has discovered or shared credit for 21 comets, including Shoemaker-Levy 9.

Levy estimates that half of all new comets are discovered by amateurs. Noting that patience is as important as a good telescope, he adds, "Comet hunting is the world's slowest sport."